The invention relates to a coupling apparatus connecting two rotatable shafts of a turbocompressor.
A bearing apparatus for a turbocompressor is known from the specification DE 26 58 687 A1. This bearing apparatus is suitable in particular for turbo machines which are designed to be very long and which have a plurality of compressor wheels which are arranged adjacently on a common shaft. The rotor shaft of this known bearing apparatus is completely electromagnetically journalled by means of electromagnetic radial bearings as well as an electromagnetic axial bearing. It is disadvantageous in this known bearing apparatus that the axial bearings have a low carrying force. In particular when a plurality of compressor wheels are arranged on the bearing shaft, relatively large force variations can arise in the axial direction, through which the known bearing apparatus could be overloaded or damaged. Further disadvantageous in the known bearing apparatus is that the axial bearing can have an unfavorable effect on the rotor-dynamic behavior of the shaft.
The object of the present invention is to create an apparatus for a turbocompressor which enables a more advantageous operation.
According to the invention, a coupling apparatus for connecting two rotatable shafts of a turbocompressor includes a first and a second coupling part which are designed for firm connection to one end section of the shafts each, as well as comprising a third coupling part which is designed in disc-shape and which is to be arranged between the first and the second coupling part. The first, second and third coupling part are firmly connectable to one another. The third coupling part has a section which projects beyond the first or second coupling part in the radial direction and which is designed as a bearing disc of an axial bearing.
The coupling apparatus in accordance with the invention has the further advantage that the bearing disc can be designed to be relatively large radially in order to produce a large force in the axial direction with the electromagnetic axial bearing. Due to the high speed of rotation of a turbocompressor, large radial forces or large centrifugal forces respectively arise at a heavy bearing disc or at a bearing disc with relative large diameter respectively. The coupling apparatus in accordance with the invention permits the bearing disc to be designed in such a manner that it is suitable for high speeds of rotation, for example for a peripheral speed of 400 m/s. In a preferred embodiment the bearing disc is designed as a through-going bearing disc, without a bore in its center. In addition the bearing disc is preferably forged. A bearing disc which is designed in this manner has the required material properties in order also to be operated safely at high speeds of rotation. In a further, advantageous embodiment the bearing disc is designed to become thinner outwardly in order to reduce its mass and thereby to achieve a constructional shape which is optimized in regard to stress.
The shaft of a turbocompressor has large radial deflections in particular in the region of the first, second, third or fourth critical resonance frequency, with the shaft developing oscillation bulges and oscillation nodes in its direction of extent. An advantage of the coupling apparatus in accordance with the invention is that through the shortening of the constructional length which results from the integration of the axial bearing disc into the coupling, a better possibility of influencing the rotor dynamics can be achieved.
The invention will be explained in the following with reference to a plurality of exemplary embodiments, with identical reference symbols relating to identical objects.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.